本周，火箭二号完成了历史性的绕月飞行，成为近54年来第一批访问月球的宇航员。
机组人员打破了人类有史以来从地球旅行最远距离的记录，并看到了比任何人都目睹的更多的月球背面。
自从美国国家航空航天局将宇航员送上月球任务已经过去了半个多世纪，许多人都在想:为什么过了这么久才返回?
天文学专家和太空历史学家告诉美国广播公司新闻，美国一直拥有重返月球的技术能力，但包括成本和优先事项变化在内的因素推迟了月球任务。
休斯顿莱斯大学的物理学和天文学教授帕特里夏·雷夫告诉美国广播公司新闻说:“最终，花费这么长时间的主要原因是它花费了很多钱。”“当我们制作阿波罗时，我们投入了5%的联邦预算，让阿波罗在很短的时间内安全出发。现在，美国国家航空航天局的预算不到联邦预算的5%,不到联邦预算的0 . 5%...所以你不可能负担得起美国国家航空航天局想做的所有事情。”
美国如何首次登上月球
1961年5月，在国会联席会议上的一次演讲中，小约翰·肯尼迪总统承诺美国将在十年内实现人类登月并安全返回地球的目标。
航天历史学家艾米·希拉·泰特尔(Amy Shira Teitel)告诉美国广播公司新闻(ABC News)，冷战期间，美国与苏联进行了太空竞赛，苏联取得了重大进展。
首先是世界上第一颗人造卫星Sputnik 1号，它于1957年10月4日发射，然后是一个月后的Sputnik 2号，它载着小狗Laika进入太空，这是第一只绕地球飞行的动物。
然后，在1961年4月12日，苏联宇航员尤里·阿列克谢耶维奇·加加林驾驶东方1号火箭和太空舱在环绕地球的单一轨道上进行了首次成功的载人航天飞行。
泰特尔说，冷战推动了美国当时登月的努力，这是美国今天没有面临的压力。
“如果没有冷战，我们就不会(登上月球)，因为这是一件疯狂的事情，”泰特尔说。“这是一场冷战式的斗气比赛，有史以来最酷的斗气比赛，但这是一场冷战式的斗气比赛。...苏联获得了所有的第一。很明显，苏联人正在开发生物系统来维持乘客的生命。”
阿波罗11号完成了肯尼迪的目标，于1969年7月20日让美国宇航员登上了月球。着陆期间，休斯顿的任务控制中心在大屏幕上闪现了肯尼迪宣布登月计划的讲话，紧接着是这样的文字:“任务完成，1969年7月。”
阿波罗任务之后
美国人又进行了五次登月，最后一次是1972年12月的阿波罗17号任务，由吉恩·塞尔南、罗纳德·埃文斯和哈里森·施密特驾驶。
阿波罗17号最初并不意味着是最后一次任务——阿波罗20号曾计划登月。但是随着预算的削减，在阿波罗17号发射的两年前，最后三次阿波罗任务已经被取消，美国太空计划改变了它的优先次序。
史密森尼国家航空航天博物馆阿波罗收藏馆馆长Teasel Muir-Harmony告诉美国广播公司新闻说:“人们有一种误解，认为阿波罗计划后，太空计划逐渐结束，但实际上它改变了方向和重点。”“在尼克松政府执政期间，它确实从国家优先事项变成了许多国家优先事项之一。”
她补充说:“人们认为，以一种更经济实惠的方式进行太空探索对中国来说将是非常重要的。”。
理查德·尼克松总统指示美国国家航空航天局少关注深空探测，多关注近地轨道任务。其中包括美国第一个轨道空间站“天空实验室”,它于1973年5月14日发射升空。
在此期间，美国国家航空航天局还开发并运行了航天飞机计划——正式名称为STS，或太空运输系统——世界上第一个可重复使用的航天器，为低地球轨道任务运送人员和货物。航天飞机计划于1968年首次设想，于1972年获得批准，首次载人航天发射于1981年4月12日进行，当时哥伦比亚号首次搭载两名机组人员乘坐STS 1进入轨道。总共有135次载人航天任务，最后一次是在2011年7月8日，当时该计划已经退役。
穆尔-哈莫尼说，1989年，乔治H.W布什总统宣布了太空探索计划，目标是重返月球“停留”，并最终执行火星任务。由于成本原因，该计划被布什的继任者比尔·克林顿总统终止，转而支持成本较低的任务。
克林顿政府致力于将名为“自由”的模块化空间站计划转化为国际空间站。，最大的人类——马
Artemis II's moon mission is the 1st in more than 50 years. Why did it take the US so long to return?
TheArtemis II crewcompleted a historic lunar flyby this week, becoming the first astronauts in nearly 54 years to visit the moon.
The crew broke the record for the farthest distance humans have ever traveled from Earth and saw more of the far side of the moon than anyone has witnessed.
Given the more than half a century since NASA sent a crew on a moon mission, many are wondering: why did it take so long to return?
Astronomy experts and space historians told ABC News that the U.S. has always has the technological capabilities to return to the moon, but factors including cost and shifting priorities have delayed a lunar mission.
"Ultimately, the main reason it's taken so long is it's cost a lot of money," Patricia Reiff, a professor of physics and astronomy at Rice University in Houston, told ABC News. "When we did Apollo, we dedicated 5% of the federal budget to make Apollo go and be safe in a very short time. Right now, NASA's budget isn't 5% of the federal budget, it's less than a half of 1% of federal budget ... and so you just can't afford everything NASA wants to do."
How the U.S. first got to the moon
In May 1961, inan address to a joint session of Congress, President John F. Kennedy Jr. committed the U.S. to the goal of landing a man on the moon and returning him safely back on Earth before the end of the decade.
The U.S. was in a space race with the Soviet Union amid the Cold War, and the Soviet Union was making significant advancements, Amy Shira Teitel, a spaceflight historian, told ABC News.
First was Sputnik 1, the world's first artificial satellite, which launched Oct. 4, 1957, and then Sputnik 2 a month later, which carried Laika the dog into space – the first animal to orbit the Earth.
Then, on April 12, 1961, Soviet cosmonaut Yuri Alekseyevich Gagarin performed the first successful crewed spaceflight when he rode the Vostok 1 rocket and capsule on a single orbit around the Earth.
Teitel said the Cold War drove America's efforts then to reach the moon, a pressure the U.S. isn't facing today.
"If it hadn't been for the Cold War, we wouldn't have [landed on the moon] because it was an insane thing to do," Teitel said. "It was a Cold War pissing contest, the coolest pissing contest of all time but it was a Cold War pissing contest. ... The Soviet Union got all the firsts. It was very clear that the Soviets were developing biological systems to keep passengers alive."
Apollo 11 accomplished Kennedy's goal, famously landing American astronauts on the moon on July 20, 1969. During the landing, Mission Control in Houston flashed Kennedy's speech announcing the commitment to the moon on its big screen,followed by the words: "TASK ACCOMPLISHED, July 1969."
After the Apollo missions
Americans went on to land five more times on the moon with the last being theApollo 17mission in December 1972, crewed by Gene Cernan, Ronald Evans and Harrison Schmitt.
Apollo 17 initially was not meant to be the last mission – there had been lunar landings scheduled through Apollo 20. But with budget cuts, the last three Apollo missions hadalready been cancelledtwo years before Apollo 17's launch, and the U.S. space program changed its priorities.
"There is a misperception that after the Apollo program, the space program wound down, but it's actually switched direction and switched focus," Teasel Muir-Harmony, curator of the Apollo collection at the Smithsonian National Air and Space Museum, told ABC News. "And it did change from becoming the national priority to one of many national priorities under the Nixon administration."
"It was decided that it was going to be important for the country to pursue space exploration in a more economically modest way," she added.
President Richard Nixon directed NASA to focus less on deep space exploration and more on low-Earth orbit missions. Among these wasSkylab, America's first orbiting space station, which launched on May 14, 1973.
During this period, NASA also developed and ran theSpace Shuttle program– officially known as the STS, or Space Transportation System – the world's first reusable spacecraft, to transport crew and cargo for low Earth orbit missions. First envisioned in 1968, the shuttle program was authorized in 1972 and the first crewed launch into space took place April 12, 1981, when Columbia carried an inaugural crew of two into orbit aboard STS 1. There were 135 crewed shuttle missions in all, the last on July 8, 2011, when the program was retired.
In 1989, President George H.W. Bush announced the Space Exploration Initiative with the goals of going back to the moon "to stay" and, eventually, missions to Mars, Muir-Harmony said. The initiative was ended by Bush's successor, President Bill Clinton, due to costs and in favor of less expensive missions.
The Clinton administration focused on converting plans for a modular space station called Freedom into theInternational Space Station., The largest human-made object to ever orbit the Earth, the ISS was constructed with the assistance of the Canadian, European and Japanese space agencies and 14 other countries. It launched on Nov. 20, 1998, and is still in use.
In 2004, President George W. Bush revisited his father's space aspirations by presenting theVision for Space Exploration Program, which included among its goals returning to the moon by 2020 and eventually sending a crewed mission to Mars.
NASA'sConstellation Programwas created in response to the goals laid out in the Vision for Space Exploration. However, after a2009 reportfound the program was so behind schedule and over budget that its goals were likely not feasible, it was canceled by Bush's successor, President Barack Obama, in 2010.
Obama'sspace policyshifted away from plans to return to the moon and instead proposed more funding for NASA and the development of a program that could eventually lead to crewed missions to Mars and other destinations.
"It's taken so long to go back to the moon because look at all of these large-scale programs behind schedule and over budget, like a theme here," Teitel said. "So, we're seeing all of these big programs, 'Oh, it's too expensive. It's over budget. It's behind schedule. We can't spend this kind of money.'"
Despite the Constellation Program being canceled, its legacy survives with the Orion spacecraft. Initially designed for the Constellation Program for use in low Earth orbit, it became the crew module used for the Artemis missions.
NASA launches the Artemis program
Dorit Donoviel, executive director of the Translational Research Institute for Space Health at Baylor College of Medicine, told ABC News that having several administrations with consistent priorities and requests of NASA is another factor that helped get the U.S. back to the moon.
In December 2017, the first Trump administrationsigned a directiverefocusing the space program on sending American astronauts back to the moon, followed by missions to Mars and potentially even farther. In May 2019, NASA named the programArtemis– in Greek mythology, the twin sister of Apollo and the goddess of the moon.
This priority continued under the Biden administration. In November 2022, Artemis Isuccessfully completed a 25-day uncrewed flightthat came within just 60 miles of the moon.
Artemis I, which tested the integrated Orion spacecraft and Space Launch System (SLS) rocket, set the stagefor Artemis II, which is the first crewed flight of Orion.
"I have to give [Trump] credit," Donoviel said. "He had the vision to get us back there. And obviously, he's been out of office in between, but he's come back to that vision. He could have changed his mind. He could have said, 'No, I don't want to go to the moon. I want to go to Mars or I want to look at an asteroid again, or I want to really focus on just low Earth orbit.' He could have done all those things, but he stuck with his original plan."
Muir-Harmony agreed that when multiple administrations from different political parties support lunar exploration, it's easier for a project to get off the ground. She cited as examples the Kennedy, Johnson and Nixon administrations supporting Apollo and the Trump and Biden administrations supporting Artemis.
"That same political support, especially at the presidential level, is pretty critical," she said. "It's important to emphasize that there were other presidential proposals to send humans to the moon before Artemis ... [but] one of the really important factors that you see that's similar about Apollo and about Artemis is that they have maintained sustained political support through multiple presidential administrations."
